package sym.qrcode.common;

public final class BitArray {

	// TODO: I have changed these members to be public so ProGuard can inline
	// get() and set(). Ideally
	// they'd be private and we'd use the -allowaccessmodification flag, but
	// Dalvik rejects the
	// resulting binary at runtime on Android. If we find a solution to this,
	// these should be changed
	// back to private.
	public int[] bits;
	public int size;

	public BitArray() {
		this.size = 0;
		this.bits = new int[1];
	}

	public BitArray(int size) {
		this.size = size;
		this.bits = makeArray(size);
	}

	public int getSize() {
		return size;
	}

	public int getSizeInBytes() {
		return (size + 7) >> 3;
	}

	private void ensureCapacity(int size) {
		if (size > bits.length << 5) {
			int[] newBits = makeArray(size);
			System.arraycopy(bits, 0, newBits, 0, bits.length);
			this.bits = newBits;
		}
	}

	/**
	 * @param i
	 *            bit to get
	 * @return true iff bit i is set
	 */
	public boolean get(int i) {
		return (bits[i >> 5] & (1 << (i & 0x1F))) != 0;
	}

	/**
	 * Sets bit i.
	 * 
	 * @param i
	 *            bit to set
	 */
	public void set(int i) {
		bits[i >> 5] |= 1 << (i & 0x1F);
	}

	/**
	 * Flips bit i.
	 * 
	 * @param i
	 *            bit to set
	 */
	public void flip(int i) {
		bits[i >> 5] ^= 1 << (i & 0x1F);
	}

	/**
	 * Sets a block of 32 bits, starting at bit i.
	 * 
	 * @param i
	 *            first bit to set
	 * @param newBits
	 *            the new value of the next 32 bits. Note again that the
	 *            least-significant bit corresponds to bit i, the
	 *            next-least-significant to i+1, and so on.
	 */
	public void setBulk(int i, int newBits) {
		bits[i >> 5] = newBits;
	}

	/**
	 * Clears all bits (sets to false).
	 */
	public void clear() {
		int max = bits.length;
		for (int i = 0; i < max; i++) {
			bits[i] = 0;
		}
	}

	/**
	 * Efficient method to check if a range of bits is set, or not set.
	 * 
	 * @param start
	 *            start of range, inclusive.
	 * @param end
	 *            end of range, exclusive
	 * @param value
	 *            if true, checks that bits in range are set, otherwise checks
	 *            that they are not set
	 * @return true iff all bits are set or not set in range, according to value
	 *         argument
	 * @throws IllegalArgumentException
	 *             if end is less than or equal to start
	 */
	public boolean isRange(int start, int end, boolean value) {
		if (end < start) {
			throw new IllegalArgumentException();
		}
		if (end == start) {
			return true; // empty range matches
		}
		end--; // will be easier to treat this as the last actually set bit --
				// inclusive
		int firstInt = start >> 5;
		int lastInt = end >> 5;
		for (int i = firstInt; i <= lastInt; i++) {
			int firstBit = i > firstInt ? 0 : start & 0x1F;
			int lastBit = i < lastInt ? 31 : end & 0x1F;
			int mask;
			if (firstBit == 0 && lastBit == 31) {
				mask = -1;
			} else {
				mask = 0;
				for (int j = firstBit; j <= lastBit; j++) {
					mask |= 1 << j;
				}
			}

			// Return false if we're looking for 1s and the masked bits[i] isn't
			// all 1s (that is,
			// equals the mask, or we're looking for 0s and the masked portion
			// is not all 0s
			if ((bits[i] & mask) != (value ? mask : 0)) {
				return false;
			}
		}
		return true;
	}

	public void appendBit(boolean bit) {
		ensureCapacity(size + 1);
		if (bit) {
			bits[size >> 5] |= (1 << (size & 0x1F));
		}
		size++;
	}

	/**
	 * Appends the least-significant bits, from value, in order from
	 * most-significant to least-significant. For example, appending 6 bits from
	 * 0x000001E will append the bits 0, 1, 1, 1, 1, 0 in that order.
	 */
	public void appendBits(int value, int numBits) {
		if (numBits < 0 || numBits > 32) {
			throw new IllegalArgumentException(
					"Num bits must be between 0 and 32");
		}
		ensureCapacity(size + numBits);
		for (int numBitsLeft = numBits; numBitsLeft > 0; numBitsLeft--) {
			appendBit(((value >> (numBitsLeft - 1)) & 0x01) == 1);
		}
	}

	public void appendBitArray(BitArray other) {
		int otherSize = other.getSize();
		ensureCapacity(size + otherSize);
		for (int i = 0; i < otherSize; i++) {
			appendBit(other.get(i));
		}
	}

	public void xor(BitArray other) {
		if (bits.length != other.bits.length) {
			throw new IllegalArgumentException("Sizes don't match");
		}
		for (int i = 0; i < bits.length; i++) {
			// The last byte could be incomplete (i.e. not have 8 bits in
			// it) but there is no problem since 0 XOR 0 == 0.
			bits[i] ^= other.bits[i];
		}
	}

	/**
	 * 
	 * @param bitOffset
	 *            first bit to start writing
	 * @param array
	 *            array to write into. Bytes are written most-significant byte
	 *            first. This is the opposite of the internal representation,
	 *            which is exposed by {@link #getBitArray()}
	 * @param offset
	 *            position in array to start writing
	 * @param numBytes
	 *            how many bytes to write
	 */
	public void toBytes(int bitOffset, byte[] array, int offset, int numBytes) {
		for (int i = 0; i < numBytes; i++) {
			int theByte = 0;
			for (int j = 0; j < 8; j++) {
				if (get(bitOffset)) {
					theByte |= 1 << (7 - j);
				}
				bitOffset++;
			}
			array[offset + i] = (byte) theByte;
		}
	}

	/**
	 * @return underlying array of ints. The first element holds the first 32
	 *         bits, and the least significant bit is bit 0.
	 */
	public int[] getBitArray() {
		return bits;
	}

	/**
	 * Reverses all bits in the array.
	 */
	public void reverse() {
		int[] newBits = new int[bits.length];
		int size = this.size;
		for (int i = 0; i < size; i++) {
			if (get(size - i - 1)) {
				newBits[i >> 5] |= 1 << (i & 0x1F);
			}
		}
		bits = newBits;
	}

	private static int[] makeArray(int size) {
		return new int[(size + 31) >> 5];
	}

	public String toString() {
		StringBuffer result = new StringBuffer(size);
		for (int i = 0; i < size; i++) {
			if ((i & 0x07) == 0) {
				result.append(' ');
			}
			result.append(get(i) ? 'X' : '.');
		}
		return result.toString();
	}

}